As a result of increased environmental consciousness, considerable attention is being directed toward electrically powered vehicles as an alternative to those designed to burn fossil fuels. Legislation is presently being considered in some jurisdictions which would require a percentage of all new vehicles to have no toxic emissions.
Most approaches to this goal involve electric propulsion. Given an electric vehicle, that is, one deriving its motive energy through an on-board electric motor, means must be provided for delivering electrical energy to that motor. If the vehicle is designed to move along a physically constrained track, which is often the case with trains, monorails and so-called "people movers," an electrical power source need not be carried by the vehicle bum, instead, may be entirely provided through inductive coupling between the track and some area of the bottom side of the vehicle. Many vehicles, including automobiles, are not designed to travel along physically exact pathways, but instead, lateral movement and speed are controlled entirely by the operator. Given the vast networks of highways throughout the world, forcing automobiles no travel in exacting tracks is an impractical goal for the foreseeable future.
Given the unpredictable movement of automobiles and other vehicles which use conventional roads and highways, electrically powered versions typically require a rechargeable battery pack to be carried on board. Given this requirement, various techniques have been proposed to recharge the batteries both between uses and during use. This requirement, various battery-powered recharging systems have been proposed, including direct connection and inductive systems operative while the vehicle is parked at a particular location, as well as systems wherein the recharging of the on-board cells is carried out while the vehicle travels along a roadway. My U.S. Pat. No. 5,311,973 "inductive Charging of a Moving Electric Vehicle's Battery" is related to such a system, as are certain of the patents issued to John G. Bolger, and others.
With the so-called "powered roadway" used in conjunction with the inductive charging of the battery in a moving electric vehicle, typically a series of primary coils are embedded on the top of the road surface, while secondary coils or some type of power pick-up device is mounted with respect to the vehicle's underbody. When the pick-up plate of the vehicle is substantially aligned with the field generator associated with the roadway, power is inductively coupled to the vehicle which is then used by the vehicle to charge its battery pack. Perhaps the most crucial problem associated with efficient coupling has to do with insuring the alignment between the roadway and vehicle counterparts or the inductive charge system, it should be obvious that the vehicle strays too far from a preferred path, power transfer will diminish. In the worst case, if the vehicle voids the powered track all together, no charging will take place and the vehicle may be stranded. It is quite important, then, to maintain consistent lateral positioning, that is, side-to-side positioning of the vehicle with respect to the preferred path along the roadway to maximize power transfer. But in addition, a valuable aspect that is typically overlooked in systems lacking a physically constrained track is the need to maintain a precise and controlled distance or "air gap" between the powered roadway and the vehicle pick-up, since, even if lateral positioning is perfect, maximum power coupling will still not occur unless the gap between the two inductive counterparts is substantially fixed as well.